Use of various inorganic binding agents such as water glass, Portland cement and the like, as well as organic type binders, e.g. synthetic resins are widely known in the manufacture of articles by casting. Despite the low cost and availability of conventional binding agents such as water glass, Portland cement, synthetic resins, they do not meet the requirements for the manufacture of articles by methods of foundry engineering.
Cold-curable mixtures based on known binding agents have the following disadvantages:
(1) on water glass: non-uniform composition, short life time and an increased residual strength after casting of cores and moulds with a molten metal which results in an impaired knocking-out of cores and moulds, i.e. extraction of castings from the moulding sand mass;
(2) on Portland cement: extended duration of hardening, impaired knocking-out;
(3) on an organic binder: increased toxicity, impaired conditions of labour for the operating personnel; furthermore, thermal sticking of sand is formed which is difficult to eliminate mechanically.
Therefore, at the present there is no cement material which would fully meet the requirements imposed on cements intended for the manufacture of cores and moulds in foundry engineering.